The invention relates to a microstructure designed for formation of a silicon and germanium on insulator substrate of Si1-XfGeXf type, with Xf comprised between a first value that is not zero and 1, and formed by stacking of a silicon on insulator substrate and a first initial layer of silicon and germanium alloy of Si1-X1GeX1 type, with X1 strictly comprised between 0 and Xf.